I have to admit that this feels like a big oversight. It completely goes against the motivation for the game, and to say it's a feature seems lazy.

I understand that the controls are supposed to be simplistic and you can play it with just a mouse. But if you're going to release a PC game you have to take things like this into consideration. It would be so much better if there were a dialogue saying "Press X to continue."

EDIT:I found a way! If you happen to complete a level by accident, instead of actually clicking the "End" button that comes up on screen, press Escape on the keyboard. This will return you to the menu screen. Then, click the level again. When it loads, it will resume where you previously left off. But you have about one second to move the object around because if you don't press anything it will just latch on to the nail again. But as long as you never click the "End" button you can keep resuming it.